You might want to consider the Red Dragon class D mono blocks, a lot of bang for the buck and gobs of power. I'm driving my 20.1s with M1000 mono blocks and they sound excellent. You should also look at the M500 as a 500 watt option. Early class D had some issues, but the new gear with improved circuitry sounds great and is quite happy driving a 4ohm load that the Maggie's require.
Regards,Doug
Regards,Doug